Arn is now a seasoned Templar, enjoying trust and respect of the grand master. His chivalrous behavior towards Muslim passersby wins him the respect of sultan Saladin, who was anonymously among them. When Saladin's army marches to besiege Jerusalem, he sends a retainer to offer Arn safe passage, which is declined. Arn correctly analyzes the enemy's best route and sets a masterly trap, which forces Saladin to retreat for the time being. Back home, Arn's beloved Cecilia gave birth to their son, which was taken away, and suffers a horror regime under the Sverker abbess. She befriends another Cecilia, who turns out the fiancée of Knut. When he comes collect her, the abbess must promise a decent treatment.

At the end of his penance term of 20 years, Templar Arn expects to return home with an honorable discharge from the late grandmaster after a last desert mission, during which he must defeat fellow knights to prevent Bedouin allies being slaughtered. The grandmaster's successor tears it up, claiming victory over Saladin is at hand and imposing foolish risks. In Sweden, his bride Cecilia is offered to succeed the wicked abbess, who dies cursing her for refusing to forgive. However she chooses to leave, visit their son Magnus, now a man, and seeking to find and marry Arn at last.